title: Origin of the Metazoa.
abstract: The origin of the multicellular animals has been investigated by rate invariant analysis of 18S rRNA sequences. These analyses indicate that (i) the Metazoa is a monophyletic taxon; (ii) the Deuterostomia is a monophyletic taxon; (iii) the Annelida-Mollusca lineage is the sister group of an arthropod subgroup; and (iv) the last common ancestor of the Annelida-Mollusca lineage is most parsimoniously derived from a segmented, hemocoelic ancestor with an open circulatory system.
authors.affiliation: Molecular Biology Institute, University of California, Los Angeles 90024.
authors.forename: J A
authors.initials: JA
authors.lastname: Lake
mesh_terms: D000828:Animal Population Groups / Q000145:classification* / Q000235:genetics; D000818:Animals; D000845:Annelida / Q000145:classification; D005075:Biological Evolution; D008974:Mollusca / Q000145:classification; D010802:Phylogeny; D012335:RNA, Ribosomal / Q000235:genetics*; D012337:RNA, Ribosomal, 18S / Q000235:genetics
chemical_list: D012335:RNA, Ribosomal; D012337:RNA, Ribosomal, 18S